In a rather short span of time—since Wednesday night—a lot of people have become converts to the view that art is an asset. They also think it is a good investment.

Rather than listen to art dealers talking their book or pundits trying to get in front of the parade based upon an outlier event, let’s listen to one of the smartest writers on investing, Jason Zweig at the Wall Street Journal.

Zweig sat down with a pencil to work out whether Leonardo’s Salvator Mundi was a good investment. Over 500 years, he found, the painting had a 1.35% annual return.

The columnist cautions that art prices go through long boom and bust cycles. So timing your entry and exit might be a little difficult.

Zweig goes on to look at that return against other asset classes using the research of Elroy Dimson and Christophe Spaenjers.

They have estimated that from 1900 through 2012, fine art produced a 2.4% average annual return after inflation, compared with 0.9% for cash, 1.1% for gold, 1.5% for bonds and 5.2% for stocks.

So a 1.35% return since 1519 is mediocre but not terrible. Between 1900 and 2016, after inflation, U.S. stocks returned 6.4% averaged annually, French stocks 3.3% and Italian stocks 2% …